I remember Gordon Myers talking about transformations (and extinction) at the 2018 BAA/AAVSO joint meeting.
He put some numbers to the size of the effect for different systems he tested (6:39)
At the end of the day though these are still approximations dependent on the actual spectrum and can be way out in some circumstances. As an extreme (though real) example, a Nova spectrum dominated by H alpha. eg
A significant fraction of the H alpha flux would appear in the standard Johnson-Cousins V passband but would be completely missed by the Chroma version. Spectroscopy is much more straightforward 😉